时间:2019-01-08 作者:英语课 分类:Scientific American(八)月


英语课

You’ve given some thought to oxygen, carbon, uranium. But you’ve probably never mused 1 about the element ytterbium, symbol Yb. A new study by scientists at the National Institute of Standards and Technology, or NIST, says that ytterbium could find a role in super-accurate atomic clocks. The report is in the journal Physical Review Letters.


 


The gold standard, if you will, for atomic clocks, is the element cesium, symbol Cs. Official civilian 2 time is kept by the cesium NIST-F1 fountain clock, accurate to within one second every 100 million years. And the international definition of the second is based on exactly how many vibrations 3 happen when a cesium atom’s electron changes energy levels. How many? 9,192,631,770. Exactly.


 


Anyway, your watch is fine for getting to work about on time, but if you want your GPS to work fine, you need these atomic clocks on Earth and on satellites. And an ytterbium clock has the potential to be even more accurate and stable than the cesium chronometer 4. Wow, I gotta go, look at the time.


 



v.沉思,冥想( muse的过去式和过去分词 );沉思自语说(某事)
  • \"I wonder if I shall ever see them again, \"he mused. “我不知道是否还可以再见到他们,”他沉思自问。 来自《简明英汉词典》
  • \"Where are we going from here?\" mused one of Rutherford's guests. 卢瑟福的一位客人忍不住说道:‘我们这是在干什么?” 来自英汉非文学 - 科学史
adj.平民的,民用的,民众的
  • There is no reliable information about civilian casualties.关于平民的伤亡还没有确凿的信息。
  • He resigned his commission to take up a civilian job.他辞去军职而从事平民工作。
n.摆动( vibration的名词复数 );震动;感受;(偏离平衡位置的)一次性往复振动
  • We could feel the vibrations from the trucks passing outside. 我们可以感到外面卡车经过时的颤动。
  • I am drawn to that girl; I get good vibrations from her. 我被那女孩吸引住了,她使我产生良好的感觉。 来自《简明英汉词典》
n.精密的计时器
  • Murchison followed with his eye the hand of his chronometer.莫奇生的眼睛追随着他的时计的秒针。
  • My watch is more expensive because it's a chronometer.我的手表是精密型的,所以要比你的贵。
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590
abasements
acetylizad
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aspergillus fischerianus
at the first blush
B synnematin
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breached fuel element
charagochilus taivanus
compound dike
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consumer information bureau
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corrigible
COSTACO
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cut per tooth
db-xx
DHKP-C
diplachne serotina link var. chinensis maxim.
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districk bank
doohickeys
dual discourse
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effects-laden
end resonance
Ephedra saxatilis
equal altitude
Erigeron morrisonensis
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four-cell type magazine loom
gentilicium
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Harbour Superintendency Administration
incomplete rupture of uterus
insociability
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Kalemyo
knee-cap
krefelds
La Condamine, Dist.
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linear light source
medalifera
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offguard
one's ears are burning
one-man atmospheric submersible
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open-endednesses
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partial track
Pereskia aculeata
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Pork-Barrel legislation
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reflectometer method
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